Prebiotics and Probiotics: How Do They Work Together?

You’ve probably heard the saying, “you are what you eat.” This is true; however, a more accurate statement would be, “you are what you feed the trillions of microorganisms that make up your gut microbiome.” This is because, like every surface of your body, the lining of your gut is covered in microscopic organisms that play an important role in your health and well-being.¹

The trillions of microorganisms that inhabit your gut are collectively known as the gut microbiota. These gut microbes (mainly bacteria) play important roles in strengthening gut integrity, harvesting energy, and regulating your immune system.^2-5

The collection of genomes represented by these bacteria is known as the gut microbiome and contains all the genetic instructions for microbial functions. Although we may not notice it’s there, the gut microbiome plays a very important role in both our mental and physical health.⁶ 

Maintaining a Healthy Microbiome Through Diet

Increasingly, the food we eat is being recognized as a key environmental factor that influences the composition and health of our microbiome.⁷ So, how can we help keep our microbiome healthy?

One way to help maintain a healthy gut microbiome is to support the beneficial bacteria already present in the gut with prebiotics.

Prebiotics

Put simply, prebiotics are compounds in food that provide a source of nutrition for gut bacteria. However, according to the good people at ISAAP (the International Scientific Association for Probiotics and Prebiotics), there is a little more to it than that.

ISAAP defines a prebiotic as a substrate that selectively promotes the growth, maintenance, and metabolism of beneficial bacteria in the gut.⁴ Importantly, this definition distinguishes prebiotics from other substances that have health benefits but are not utilized by only the host microbiota and excludes substances that can be used to support pathogenic bacteria.

A common misconception about prebiotics is that they are the same thing as dietary fiber. However, because dietary fiber does not have the prebiotic requirement of selective metabolism, it includes many substances that don’t fit the current definition of prebiotics or confer the same health benefits.^8,9

Examples of well-researched prebiotics include inulin, fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS). Although these prebiotics naturally exist in a variety of foods, it may be at concentrations too low to provide a prebiotic effect for individuals who do not consume a variety of plants. ¹⁰

• Inulin: a starchy substance found in a wide variety of fruits, vegetables, and herbs, including wheat, onions, bananas, leeks, artichokes, and asparagus.¹¹
• Fructo-oligosaccharides (FOS): a type of carbohydrate composed of short fructose chains and naturally present in plant-based foods including garlic, onion, leeks, chicory root, Jerusalem artichokes, and bananas.¹¹
• Galacto-oligosaccharides (GOS): a group of carbohydrates consisting of short chains of galactose molecules (a type of sugar found in milk) that can be found naturally in dairy products, beans, and certain root vegetables. ¹¹

Another distinguishing feature of prebiotics is that they are not digestible by the host. Instead, prebiotics pass through the digestive system where they become food for the bacteria and other microbes in the gut.⁴ 

Microbes in the gut then use this nutrition to generate short-chain fatty acids (SCFAs), which play integral roles in gut and immune health.¹² What’s more, because SCFAs are small enough to enter the blood circulation, prebiotics can benefit other distant site organs and systems, such as the central nervous system, immune system, and cardiovascular system.¹³

Prebiotic Health Benefits

Research suggests that prebiotics may support overall health through their ability to:

• Promote digestion and bowel regularity^{14, 15}
• Reduce the incidence of immune-related skin conditions^16,17
• Improve measures of skin health^16-18
• Promote a healthy antibody response to vaccines^19-21
• Help regulate neurological functions^22,23
• Improve cognitive performance^24,25
• Help decrease circulating levels of cholesterol²⁶
• Enhance calcium absorption²⁷

Probiotics

Another way to support a healthy gut microbiome is by adding living microbes directly into your system through a probiotic supplement or foods containing beneficial bacteria.

Probiotics are live bacteria and yeasts that, when consumed in adequate amounts, provide benefits for immune and digestive health.²⁸ They can be found in natural sources, such as fermented and cultured foods, or supplemental forms such as liquids, powders, and capsules.

Probiotic Health Benefits

Research suggests that probiotics may help support a healthy gut microbiome through their ability to:

• increase the number of healthy microbes in the gut²⁹
• stimulate immune functions and responses²⁹
• compete with pathogenic bacteria for nutrients²⁹
• enhance the integrity of the mucosal barrier³⁰ and
• block adhesion sites for unhealthy bacteria³¹

For a deeper dive into what probiotics are, and how they can benefit health, check out one of our other articles:

Probiotics 101: Everything you need to know

Probiotics: How Many CFU do I Need?

Can Taking Probiotics Help Support a More Positive Mood?

Help Maintain A Healthy Body Composition with Probiotics

Is it Better to Eat Probiotic Foods or Take a Probiotic Supplement?

Synbiotics

A third (and arguably, the most effective) way to maintain a balanced and healthy microbiome is by consuming prebiotics and probiotics. A simple way to achieve this is by taking a probiotic supplement with added prebiotics.

When used with probiotics, prebiotics are termed “synbiotics” and can help improve the viability of probiotics. More specifically, it has been proposed that prebiotics aid probiotics improving their survival during passage through the upper gastrointestinal tract, facilitating more efficient implantation in the colon, and providing a stimulating effect on probiotic growth.³²

Because the word synbiotics alludes to synergism (when the interaction of two or more substances produces a combined effect greater than the sum of their separate effects), this term should be reserved for instances where the prebiotic compounds selectively favor the probiotic organisms involved.³³ Synbiotic formulations often include various species of Lactobacilli and Bifidobacteria along with FOS, GOS, inulin, or some other type of prebiotic fiber.³²

Synbiotic Health Benefits

Research suggests that the combination of prebiotics and probiotic may support human health by:

• supporting healthy liver function³⁴
• regulating the body’s immune response³⁴
• improving the viability and successful implantation of probiotic bacteria³²
• increasing levels of lactobacilli and bifidobacteria³⁴
• preventing the passage of bacteria from the gastrointestinal tract to other sites in the body³⁴

In Closing

The foods we eat are continually being recognized as an important environmental factor that influences the state of the microbiome, and thus our health more generally. Talk to a nutritionist or healthcare professional about whether your diet is setting you up for success, or whether a probiotic supplement with added prebiotics would help steer you along the path to optimal health and wellness.